1. Field of the Invention
The present invention relates to a squeegee for use in screen printing, and a screen printing method, and in particular to the art of performing screen printing on a surface of an object that has at least one projection.
2. Related Art Statement
Screen printing is performed using a screen and a squeegee. A screen having a plurality of print holes is placed on an object such as a printed circuit board, a print material such as a creamed solder or an adhesive is placed on the screen, and a squeegee is moved relative to the screen placed on the object, so that the print material is forced through the print holes of the screen onto one or more print spots on a print surface of the object. In the case where the print surface of the object has one or more projections, the screen may be one which has one or more embossed portions capable of accommodating the one or more projections, respectively, and accordingly does not interfere therewith. In the case where the object is a printed circuit board, the one or more projections of the object may be one or more electric components mounted on the circuit board, or one or more projections needed for easier production of the circuit board. In the case where the object has one or more projections and the screen has one or more embossed portions for accommodating the one or more projections, one or more portions of the squeegee that correspond to the one or more embossed portions of the screen climb over the one or more embossed portions, while the remaining portion or portions of the squeegee continue to contact the screen so as to force the print material through the print holes of the screen onto the object. Thus, the print material is printed on the object.
However, when a climb-over portion of the squeegee climbs over an embossed portion of the screen, a space is created between the screen and each of two adjacent portions of the squeegee on both sides of the climb-over portion of the same. More specifically described, when the climb-over portion of the squeegee climbs over the embossed portion of the screen, distant portions of the squeegee that are sufficiently distant from the climb-over portion in a direction perpendicular to the direction in which the squeegee is moved relative to the screen, and parallel to the plane of the screen, can continue to contact an embossment-free portion of the screen that is free of embossment, but the two adjacent portions of the squeegee that are near to the climb-over portion are separated from the screen by being pulled by the climb-over portion climbing over the embossed portion of the screen. Thus, on both lateral sides of the embossed portion of the screen, respective spaces are created whose dimensions increase in respective directions toward the embossed portion. Therefore, if there is a print spot on a lateral side of, and in vicinity of, a projection of the object to be printed, the print material may not be printed on the print spot of the object.